The present invention relates to Lactobacillus gasseri (sometimes referred to as L. gasseri hereinafter) with an effect on the disinfection of Helicobacter pylori (sometimes referred to as H. pylori hereinafter) and/or the protection against infection with H. pylori, and a food or drink product containing the lactic acid bacterium.
Since the discovery of H. pylori as a bacterium living in stomach in 1983 by Warren et al. [Lancet, I. 1273 (1983)], attention has been focused on the relation with chronic gastritis, gastric ulcer and duodenal ulcer. Recently, it has been evidenced that gastric gland cancer occurs in mongolian gerbil infected with H. pylori, with no administration of any carcinogenic substance [Watanabe et al., Gastroenterology, 115; 642 (1988)] and the relation of H. pylori with gastric cancer has also been suggested as one etiological bacterium thereof.
Meanwhile, it is increasingly indicated that the disinfection of H. pylori in H. pylori-positive patients with digestive ulcer can suppress the recurrence of digestive ulcer and therefore, active disinfection therapy of H. pylori has been practiced in European counties and the U.S. As to the method for disinfecting H. pylori, a combination method of antibiotics (xcex2-lactams, aminoglycosides, macrolides, tetracyclines and the like) and antiulcerative agents is general; for example, a combination therapy of three drugs, namely two types of antibiotics (clarithromycin-metronidazole or amoxycilin) and a proton pump inhibitor (PPI) suppressing the secretion of gastric acid, is clinically practiced. However, the most serious drawback of the administration of drugs such as antibiotics for the purpose of the disinfection therapy is the increase of the frequency of the occurrence of drug-resistant H. pylori and the occurrence of severe side effects such as diarrhea and allergy and the like, due to the multiple combination of high-dose drugs.
For the purpose of the disinfection of H. pylori in stomach in place of antibiotics, examinations have been made about the method comprising administering lactoferrin (Japanese Patent Laid-open 130164/1998), the method using specific antibodies recovered by the immunization of chicken with the urease and flagellum of H. pylori as antigens (Japanese Patent Laid-open 287585/1998), and the methods comprising administering the viable bacteria of specific individual bacterial strains of Lactobacillus brevis and/or Lactobacillus salivarius (Japanese Patent Laid-open 241173/1997) and Lactobacillus acidophilus (Japanese Patent Laid-open 98782/1994), as methods using lactic acid bacteria. However, no satisfactory method has been reported yet.
On the other hand, since lactic acid bacteria generate preferable flavorful substances and have abilities to generate antibacterial substances such as lactic acid and bacteriocin, lactic acid bacteria are extremely safe microorganisms on traditional diets in the form of fermented milk and the like worldwide. Accordingly, it can be said that the disinfection of H. pylori utilizing the antibacterial action of lactic acid bacteria is a simple and effective method with no occurrence of side effects.
In the existing inventions, however, the selection of lactic acid bacterial strains, particularly Lactobacillus brevis and/or Lactobacillus salivarius (Japanese Patent Laid-open 241173/1997) has been carried out, not only with no consideration of the characteristic property of stomach environment (with resistance to the environment at low pH) as the target site of H. pylori but also with no attention paid on the properties (the survival, flavor, physical properties of the lactic acid bacterial strains) as food products prepared by using such lactic acid bacterial strains, such as fermented milk. Additionally, a report tells that Lactobacillus acidophilus used at a clinical test was consequently ineffective [Bazzoli et al., Gastroenterology, 102, No.4, A38, (1992)]. Alternatively, the results of a clinical test using the culture supernatant of the bacterial strain L. acidophilus La1 disclosed in Japanese Patent Laid-open 98782/1994 indicate a possibility of the disinfection of H. pylori but never demonstrate that the effect might be sustained [Michetti et al., Gastroenterology, 108, No. 4, A166, (1995)]. As described above, the existing lactic acid bacteria have currently more rooms to be modified so as to prepare the intended composition for the disinfection of H. pylori. 
In such current status of the industry demanding the establishment of a system for the disinfection of H. pylori/the protection against infection with H. pylori in respect to anti-gastritis and anti-gastric ulcer, the present inventors have again drawn their attention toward lactic acid bacteria from the standpoints of safety profile and oral intake and have intended to develop a system for the disinfection of H. pylori/the protection against infection with H. pylori by using lactic acid bacteria.
More specifically, the problems to be solved by the invention are to select a lactic acid bacterial strain with high survival and a great colonization property in stomach, an apparent anti-H. pylori activity in animal model experiments and marked properties (the survival, flavor and physical properties of the lactic acid bacterial strain) for use in food products such as fermented milk and provide a new food or drink product, inexpensive and daily ingestible, using the lactic acid bacterial strain, for the purpose of the disinfection of H. pylori and the protection against infection with H. pylori.